1. Field of the Invention
The present invention relates to an audio transmission line and a headset; in particular, to an audio transmission line and a headset with capabilities of switching the transmission order of the input signals.
2. Description of Related Art
Generally, when the user wants to hear the audio sounds of an electrical device (such as a mobile phone, an MP3 player, or a PDA, etc.), besides using the speaker of the electrical device, he or she may connect the audio transmission plug of a headset to the headset socket of the electrical device, which allows the speaker of the headset to play the audio signals transmitted from the electrical device. Along with the improvement of the technology, the audio transmission plugs of the headset may be classified into two types: three-section type and four-section type, and each section may be a signal transmission unit. Presently, the headset socket of the electrical device usually has four signal coupling ends, for being corresponded to the four-section type audio transmission plug, which allows each signal transmission unit to carry different headset signals. In this case, the headset signals carried by the signal transmission units may be a left sound track signal, a right sound track signal, a microphone signal, and a ground signal.
Take the mobile phone as an example, although the size of the headset socket has its standard specification, the definitions of four signal coupling ends may be different among various of manufacturers. For example, part of the mobile phone manufacturers may be used to transmitting left sound track signals by using the first signal coupling end of the headset socket (which corresponds to the first signal transmission unit of the audio transmission plug of the headset), while other manufacturers uses the same headset socket for transmitting the microphone signals.
That is, the transmission order of headset signals may be various among different manufacturers. However, because the inner circuits of the conventional headset are fixed, if the first signal transmission unit is predetermined to connect with the left side speaker, apparently, the left side speaker can only correctly interpret left sound track signals, rather than microphone signals. On the other hand, if the first signal transmission unit is predetermined to connect with the microphone component which can only correctly interpret the microphone signals rather than left sound track signals.
In order to solve the problem of the difference of the transmission order, the R.O.C. invention patent I324891 discloses a headset which may read several kinds of headset signals, which its main content is shown in FIG. 1. As shown in FIG. 1, the headset device 9 in the patent I324891 has an audio transmission plug 90 and several sets of switches SW1 to SW4. The signal transmission unit 902 is correspondingly connected with switch SW1, similarly, the signal transmission units 904 to 908 are respectively connected with the switch SW2 to SW4 one-to-one. In addition, the audio transmission plug 90 may receive the left sound track signals, the right sound track signals, the microphone signals, and the ground signals from the mobile phone through the signal transmission units 902 to 908.
In this case, the patent I324891 claimed that due to the uncertainty of the order of left sound track signals, right sound track signals, microphone signals, and ground signals (which depend on the specifications of manufacturers), there may be sixteen types of modes of signal transmission of the headset device 9. Take switch SW1 for example, it may freely output the headset signals carried by the signal transmission unit 902 as left sound track signals LCH, right sound track signals RCH, microphone signals MIC, or ground signals GND, depending on which signals are accepted by the headset. That is, patent I324891 solves the problem of headset signal transmission order by allowing the four switched to output all of the left sound track signals LCH, the right sound track signals RCH, the microphone signals MIC, and the ground signals GND.
However, seeing from the aspects of practical using and manufacturing, implementing the sixteen switch types shown in patent I324891 (especially in FIG. 3), which makes the four switches output the four acceptable signals (LCH, RCH, MIC, and GND) respectively by only the mechanical and structural operations, is apparently impossible. We can know from line 11 of page 9 of the patent I324891 that it needs to install an extra control signal generator for generating control signals, and uses the control signals to shift the transmission modes the four switches. In other words, the patent I324891 actually uses an IC chip to control the four switches for selecting the sixteen transmission modes.
A person skilled in the art may know that it is hard for a user to select the correct signal transmission mode from the sixteen modes (especially when the user does not know what the differences between the several signal transmission orders are). In addition, if the headset need to include the IC chip, its manufacturing cost increases, and there may also need extra battery or power line for providing electric power to the IC chip, which makes the headset lack of competitiveness.
It's worth noting that, the R.O.C. disclosure No. 201143226 discloses a headset which claims to be able to implement the switch signal circuit by mechanical and structural operations. However, as shown in lines 11 to 14 of page 9 of the disclosure, it only discloses the techniques of switching the audio transmission plug between three-section type and four-section type, and does not solve the problem of signal transmission order. Moreover, because the structure shown in the disclosure is too simple, one skilled in the art cannot implement more complex switching by referring to both the patent I324891 and the disclosure 201143226.
Therefore, solving the aforementioned problem of the transmission order of the headset signals is still a goal to be achieved.